Lamp sealing apparatus



1941' A. E. KULBERG ET AL 10 'LAMP' SEALING APPARATUS Filed Jan 2, I 1941 L/AZAZ//// FE 2mg 2 H HHHUI] IO August E.Kul berg AND Ral bh Thomas, INVENTORS W l k-m,

ATTORNEY Patented Dec. 30, 1941 LAMP SEALING APPARATUS August E. Kulberg and Ralph B. Thomas, Beverly, Mass., assignors to Hygrade Sylvania Corporation, Salem, Mass., a corporation of Massachusetts Application January 2, 1941, Serial No. 372,876

4 Claims.

This invention relates to the sealing of electric gaseous discharge devices and more particularly to a means for obtaining such a seal.

An object of this invention is to obtain an even fusion of the mount and the bulb of an electric gaseous discharge lamp.

Another object is to push together the softened glass of the mount and the bulb so that a seal may be formed.

Another object is this type of lamp.

A further object is to provide a means for controlling the stretching of the seal while the portions being fused are still soft and pliable.

Further objects, advantages and features will be apparent from the specifications which follow taken in conjunction with the accompanying drawing in which:

Figure 1 is a side elevational view of the mount pin pusher assembly shown partly in section.

Figure 2 is detail of the mount pin pusher shown in section.

Similar reference characters refer to similar parts in the several views of the drawing and in the specifications which follow.

In the manufacture of electric gaseous discharge lamps it is extremely important that the ends of the bulb be properly sealed. This seal is formed by a fusion of a part of the neck or the bulb with a portion of the flared part of the mount. It is for the attainment of this type of seal that this invention was devised.

The refractory cup I is suspended from collar [5. The refractory mount pin 8 is fitted in the refractory cup I in a manner as to allow free movement of the pin vertically but not horizontally. The refractory flange l5, forming the top of the refractory mount pin 8 provides a seal for the ring 2, which may be of carbon orof a metal which will not seal to glass when heated. It is on this ring 2 that the mount 3 is placed, with the exhaust tube, if there is one, and lead-in wires extending down inside the pin 8. The lamp bulb 4 must be held firmly in position for two reasons: first, so that it will not move or press down by reason of its own weight on the molten glass when it is being heated for sealing purposes; and second, so that it will be capable of resisting the upward pressure of the mount pin pusher.

The conductor coil I4 shown encircling the refractory cup I may be of edgewise wound copper ribbon, or hollow copper tubing. This coil is energized by passing through it a current of high frequency, say one million cycles per second.

to obtain a well knit seal in This heats the carbon ring 2 by induction, the ring acting as a single closed turn of a transformer. The ring may thus be heated to temperature sufficient to fuse the bulb 4 and the enough, the seal would not be a strong tight one.

If the glass were stretched too much, the seal would be too thin; and if it were not stretched enough, the seal would not be an even one or else it would not be a strong tight one and it would be apt to crack. Stretching and working the glass relieves strains.

It is for -this purpose that I have devised a mount pin pusher which may be adjusted to work and stretch the seal as desired. It may be mounted on an auxiliary carrying plate l3 which may be moved to the position shown in Figure 1 when the seal is to be compressed, and which may be moved vertically downward and out of the way while the glass is being softened before compression. The mount pin pusher assembly as shown in Figure 1 has been moved up to aid in sealing the mount to the bulb. A better understanding of just how it operated may be obtained by a study of Figure 2, a cross-section of the mount pin raising mechanism. This mechanism consists of the limiting rod 5 which is threaded into the plate l0, said plate having the cylindrical stud 6 freely mounted in the bushing l l is shouldered at its lower extremity to allow a bearing surface for the spring 9 within which the stud of the plate may move. spring 9 is retained by the cap I! which shoulders the spring and is freely fitted in the counterbored upper extremity of the bushing II. This cap I! is firmly fixed to the top of the stud 8, thus limiting the downward motion of .the stud 6 to the extent to which the bushing II is counter-bored. The mount pin pusher mechanism in Figure 2 shows the relative location of the parts before the mechanism moves up to act on the mount and'bulb. It shows the plate Ill flush with the bushing H, the cylindrical stud 5, mounted on top of the plate l0, projecting upward from the top of the bushing II, and the spring 9 in a partially expanded state due to the fact that The upper extremity of the the limiting rod no pressure is being exerted on it by the mount pin 8.

The position which the parts may assume when the device is in operation is shown in Figure 1. Whenthis mount pin pusher assembly has been moved up until the pin pusher I strikes the bottom of the mount pin 8, the glass will probably still not be soft enough to permit any substantial compression thereof. In this ca se, the pin pusher I will be pushed downward by the mount pin 8 and the spring 9 will be compressed thereby because the tension of the spring 9 is calculated to exert a pressure'only slightly greater than that necessary to lift the dead weight of the carbon ring I, the mount pin 8 and the mount 3. However, the glass soon becomes so soft that the spring gradually expands and thus pushes the mount pin 8 upward until the limiting rod 5 strikes the cup I. When this occurs, the flange I 8 originally seated position substantially as shown in Figure 1.

As mentioned above, this mechanism is devised not only to compress the molten glass to form the seal, but it is also used to limit the drop of the seal after it has been formed. It is desirable to stretch the seal but yet not let it sag or drop down too far. In the compressing of the molten glass to form the seal originally, served as a means of limiting the extent of the compression; in the stretching of the seal, the limiting rod 5 acts as a means of controlling the height of the flange I6 which in turn limits the drop of the seal after it has been formed.

After the glass has been compressed as much as desired, some means must be found to prevent the seal from sagging and dropping down too far because at this stage, the glass is soft enough to sag and drop. This is accomplished by adlusting the height of the limiting rod 5 so that it will not strike the bottom of the cup I until the mount pin pusher 6 has pushed the mount pin I upward far enough to raise the flange I8 oil. the seat of cup I and hold it at the point beyond which it is not desired that the seal be stretched. The carbon ring 2 has a tendency to stick to the seal and the weight of this ring 4 pulling on the molten glass will stretch the seal until the carbon ring 2 comes to rest on the top of the flange I8 which flange has been projected up from its position flush on the seat of the cup I to limit this dropping of the seal. Thus the seal can drop no further.

The advantage of this device which combines on the cup I will be up in the a pin pushing means with a limiting means is that when it is used there are but two possible factors which might aflect is accuracy and both of them may be adequately cared for with but little eifort. One is the thickness of the base of the cup I and the other is the length of the mount pin 8 under the shoulder thereof. Both the cup and the pin may be machined to a fine degree of precision before they are ever used. Because of this, the larger parts of the machine to which the cup may be fixed may have greater without affecting the accurate contolerances trolling of seal.

What I claim is:

1. In a lamp sealing machine: a bushing, a stud extending through said bushing and movable with respect thereto, a plate aillxed to said stud, a spring pushing said stud upward through said bushing, and a limiting rod fixed to and extending upward from said plate.

2. In a lamp sealing machine: a bushing, a stud extending through said bushing and movable wlth respect thereto, a plate aflixed to said stud, a spring within said bushing and pushing said stud upward, a cap for retaining said spring, an adjustable limiting rod fixed toand extending upward from said plate.

3. In a lamp sealing machine having a mount pin extending down through the bottom of the cup through which it is fitted: a bushing, a stud extending through said bushing and movable with respect thereto, a plate on which the lower extremity of said stud is mounted, a spring so located as to project said stud upward against said mount pin, and an adjustable limiting rod attached to said plate therefrom in the direction of said cup.

4. In a lamp sealing machine having a refractory cup and a mount pin extending down through the bottom of said cup through which it is fitted: a bushing, a stud extending through said bushing and movable with respect thereto, a plate on which the lower extremity of said stud is mounted, a spring so located as to project said stud upward against said mount pin, and an adjustable limiting rod attached to said plate and projecting upwardly therefrom to a height sufficient to strike the bottom of said cup thus limiting the distance through which said spring may project said stud;

AUGUST E. KULBERG. RALPH B. THOMAS.

the compressing and stretching of the and projecting upwardly 

